1. Field of the Invention
This invention relates to the field of redundant cable control and standby control systems. More specifically this invention relates to apparatus which implements a bypass cable control system in the event of primary control system cable failure.
2. Description of the Prior Art
Engine rotor or propeller failure in aircraft can cause debris to fly through the body of the aircraft and sever control cables. Airworthiness authorities have indicated that the catastrophic hazards resulting from such severed control cables are uncertifiable conditions. As a result design precautions must be taken on all new aircraft, and all old aircraft design to minimize the risk from control cable severing. On totally new designed aircraft the solution was to route one cable loop of the redundant loops out of the un-contained debris path, such as routing one of the redundant pair of the primary control cables through the ceiling of the aircraft from the cockpit to the control surfaces while routing the other through the floor. This solution is impractical and costly on derivative aircraft that must meet the certification requirements due not only to the installation practicability, but also due to the adverse effect on the control system, such as break-out friction and control wheel harmony. The prior art is replete with redundant flight control systems of various kinds. These prior art devices are typified by U.S. Pat. No. 4,776,543 to STABLEFORD and U.S. Pat. No. 3,599,507 to EXTON. These prior art devices rely on sensing the severing of the primary cable as the means for sensing failure and then operate with the remaining cable. None of the prior art devices will operate when all of the cables are severed, which is likely when the cables are located in the same region. None of the prior art devices use a separate sensing mechanism and therefore excessive slack in the cable can cause an indication of failure when none has occurred.